Electromagnetic field quantization in an absorbing medium

A three-dimensional electromagnetic field quantization scheme is developed using the Green's-function method in a homogeneous medium that shows loss and dispersion. Special attention is paid to the decomposition of the quantized fields into their longitudinal and transverse parts. The characteristic nature of these two parts is discussed. To demonstrate the generality of this formulation, the field quantization in lossless dispersive media and in free space is obtained by imposing appropriate limits. We also calculate the vacuum fluctuations of the field for the transverse and longitudinal parts separately.